Stylus detection with capacitive based digitizer sensor

Abstract

A method for detecting a signal transmitted by a handheld device includes detecting a signal on first electrodes along a first axis and on second electrodes along a second axis of the digitizer sensor. The method additionally includes detecting hand input on the first electrodes and on third electrodes along the second axis and detecting no hand input on the second electrodes. The hand input detection is based on self-capacitive detection. The signal transmitted by the handheld device on the first electrodes is estimated based on the hand input detected on each of the first and third electrodes, the signal from the handheld device detected on the second electrodes and based on a pre-defined constant. Coordinates of the handheld device are determined based on the signal detected on the second electrodes and the signal estimated. The coordinates are reported to a host computing device associated with the digitizer sensor.

What is claimed is: 
     
       1. A method comprising:
 detecting a signal on first electrodes along a first axis of a digitizer sensor and on second electrodes along a second axis of the digitizer sensor, wherein the signal is a signal transmitted by a handheld device interacting with the digitizer sensor; 
 detecting hand input on the first electrodes and on third electrodes along the second axis and detecting no hand input on the second electrodes, wherein the hand input detection is based on self capacitive detection; 
 estimating the signal transmitted by the handheld device on the first electrodes as a pre-defined constant multiplied by a peak gain of the signal on the second axis and by a ratio of finger effects detected from the hand input, wherein the ratio is a first finger effect along the first axis over a second finger effect along the second axis; 
 determining coordinates of the handheld device based on the signal detected on the second electrodes and the signal estimated on the first electrodes; and 
 reporting the coordinates to a host computing device associated with the digitizer sensor. 
 
     
     
       2. The method of  claim 1 , wherein the pre-defined constant is an inter axis impedance ratio. 
     
     
       3. The method of  claim 2 , wherein the ratio is defined based on accumulated empirical data detected while a hand is coupled to sensing lines along one axis that carry a stylus signal and not coupled to sensing lines along the other axis that carry a stylus signal. 
     
     
       4. The method of  claim 2 , wherein the ratio relates output detected during stylus detection and corresponding output detected during self-capacitive detection. 
     
     
       5. The method of  claim 2 , wherein the pre-defined constant is defined for a specific touch enabled computing device. 
     
     
       6. The method of  claim 2 , wherein the pre-defined constant is stored in the host computing device or in a circuit associated with the digitizer sensor. 
     
     
       7. The method of  claim 1 , comprising evaluating interference due to the hand input and initiating the estimating based on determining that the interference is above a defined threshold. 
     
     
       8. The method of  claim 7 , wherein the evaluating is based on comparing detected peak energy of stylus signal on each of the axis. 
     
     
       9. The method of  claim 8 , comprising estimating the grounding state of a device including the digitizer sensor based on the comparing. 
     
     
       10. The method of  claim 7 , wherein the evaluating is based on a parameter defining jitter during tracking. 
     
     
       11. The method of  claim 1 , wherein the first finger effect along the first axis is an array of finger effects. 
     
     
       12. The method of  claim 1 , wherein the second finger effect along the second axis is a peak finger effect detected with output from the self-capacitive detection. 
     
     
       13. The method of  claim 1 , wherein the signal estimated on the first electrodes is an array signals, from which a coordinate along the first array is determined.